We are considering the same thing as well. (Change our porch to a sunroom and include a full bath). We have started talking to designers to help us plan and cost it out. We'll decide when we see the cost. If all goes well, we'll use the room as a family room and when guests come over, it will transition into a guest room - think murphy and pull out beds. If we find someone who can do it, we might even still be able to use it as a porch with large glass sliding doors... (now, this last sentence is the pie in the skies part of me talking. Contractors just give me funny looks when I present my vision to use the space in three ways. Wish me luck!)